DIY desk synth without arduino

[Reza]

Hi I'm making a DIY desk synth without an Arduino.
I have a midi keyboard smk25 with midi out into opto isolator then a dac then an opamp.
I want to play the notes on the keyboard and hear the note out the speaker.

Can someone please help me along the way with building it.
So after opto what do I need I can see the note on the oscilliscope and the led lights on note on and lights on note off.

[Grumble]

https://github.com/probonopd/MiniDexed

https://github.com/probonopd/MiniDexed/discussions

https://youtu.be/S6fjJ5Is0pg?si=QOy7bRoD8h-PsDau

I guess this will help you out!
Its not with an arduino, but uses an Raspberry Pie instead.

[analogmonster]

If you try to avoid microcontrollers and programming in general you will need to do an exception with your MIDI interface AFTER the opto coupler.

[Reza]

Just some images and a video of my circuit

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VID_20251211_125106976.mp4
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[Reza]

Optoisolator
Dac
Opamp

[Reza]

ive had to remove the 9v battery from the rails and use it to power the opamp
i need to get another 9v battery